University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 12-2016 ASSESSING THE FUNCTIONAL SIMILARITY OF NATIVE AND INVASIVE ANOLIS LIZARDS IN THE FOOD WEBS OF STRUCTURALLY-SIMPLE HABITATS IN FLORIDA Nathan W. Turnbough University of Tennessee, Knoxville, [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Part of the Terrestrial and Aquatic Ecology Commons Recommended Citation Turnbough, Nathan W., "ASSESSING THE FUNCTIONAL SIMILARITY OF NATIVE AND INVASIVE ANOLIS LIZARDS IN THE FOOD WEBS OF STRUCTURALLY-SIMPLE HABITATS IN FLORIDA. " PhD diss., University of Tennessee, 2016. https://trace.tennessee.edu/utk_graddiss/4174 This Dissertation is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a dissertation written by Nathan W. Turnbough entitled "ASSESSING THE FUNCTIONAL SIMILARITY OF NATIVE AND INVASIVE ANOLIS LIZARDS IN THE FOOD WEBS OF STRUCTURALLY-SIMPLE HABITATS IN FLORIDA." I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Doctor of Philosophy, with a major in Ecology and Evolutionary Biology. Arthur C. Echternacht, Major Professor We have read this dissertation and recommend its acceptance: David A. Buehler, Susan E. Riechert, Daniel Simberloff Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) ASSESSING THE FUNCTIONAL SIMILARITY OF NATIVE AND INVASIVE ANOLIS LIZARDS IN THE FOOD WEBS OF STRUCTURALLY-SIMPLE HABITATS IN FLORIDA A Dissertation Presented for the Doctor of Philosophy Degree The University of Tennessee, Knoxville Nathan W. Turnbough December 2016 Copyright © 2016 by Nathan W. Turnbough All rights reserved. ii ACKNOWLEDGEMENTS The work presented in this dissertation would not have been possible without the support and assistance of a great number of people. Chief among them is my advisor, Sandy Echternacht. Sandy’s support for me was unwavering, despite my many failings and periods of stymied progress, and I am grateful for the level of patience and optimism he showed to me through it all. Sandy was always quick to provide whatever assistance he could—guidance in study design, rushing supplies to me in the field, helping to catch lizards and arthropods, and myriad other forms of assistance—, and he provided most of the logistical and financial support for this project. I am very much appreciative of the time and energies he devoted towards my success as a scholar. The spoils islands were a wonderful system to work in, and I am deeply indebted to Mike Legare (Merritt Island NWR) and John Stiner (CANA) for graciously granting me permits to work on them; Mike also assisted me in finding a field site for the palm enclosure study. I thank Todd Campbell for establishing the spoils islands as a study system, and for the guidance and advice he gave to me concerning them. I also want to thank Ross Hinkle (Dynamac) for setting up my first boat ride to the islands. I was fortunate to work in the field with Daniel Schilling, Duncan Adams, Matt Jones, Brian Freer, Andrew Jennings, and Matt Fullerton. In addition to their hard work in often adverse field conditions (Mosquito Lagoon is not an empty threat), I am grateful for the camaraderie they provided. Wendy Futrell, Dan Houlihan, Greg Johnson, Ryan Seddon, and Jessy Wilson spent many long hours in the lab processing arthropod samples for this project, for which I offer my iii sincere appreciation. I also want to express thanks to the many others who provided assistance in the field or lab for related aspects of this dissertation research: Morgan Braxton-Sears, Joe Burgess, Alfonso Dominguez, Katherine Ellenberg, Dan Estabrooks, Adam Fuller, Jessica Hentche, Jessica Hite, Sona Pastel-Daneshgar, Tyler Pannell, Catherine Stewart, Cheryl Turnbough, Donald Turnbough, and Uchung Whang. I am appreciative of the technical guidance that I received from a number of people. Matt Fitzpatrick showed me how to extract habitat data from digital island images. J.P. Lessard introduced me to the advantages of community-level analyses, which started me down a path that eventually lead to great improvements in the quality of my analyses. Jim Fordyce offered helpful statistical advice when I was uncertain about the way forward. I am also appreciative of the time and guidance given to me by members of my committee: Dan Simberloff, David Buehler, and Susan Riechert. I thank Susan for stepping in at the last moment and Nate Sanders for serving on my committee for as long as he could. I also offer thanks to members of the Graduate Affairs Committee and to Julie Harden, who gave me an opportunity to finish. Funds for this project were supplied in part by the Department of Ecology and Evolutionary Biology (EEB) and the American Society of Ichthyologists and Herpetologists; EEB also kindly lent me the use of a boat for the entirety of this project. I could not have finished this dissertation without the kind assistance of Cheri Hall, Michelle Thress, and Barbara Turnbough, who freed up many additional work hours for me during several critical stages of the writing process. Finally, I would like to thank my family for the many sacrifices they made, including a scarcity of quality family time, as their tired and distracted father/husband made an all-out effort iv to finish this dissertation. I owe a special debt of thanks to my wife Jess, who tolerated my long absences and gave me a great deal of financial and moral support, especially towards the end. v ABSTRACT Invasive species often displace ecologically-similar native species, but the extent to which invading and displaced species function similarly in the food web processes of invaded communities is largely unknown. I investigated whether populations and individuals of an invasive Anolis lizard (the brown anole, Anolis sagrei) and the native congener it displaces in Florida (the green anole, Anolis carolinensis) are functionally equivalent in the food webs of open and structurally-simple habitats. In a system of invaded and uninvaded dredge-spoils islands, I found that both arthropod communities and winter bird communities covaried with brown anole abundance (and therefore the identity of the dominant anole species operating in island food webs) in ways that were generally well explained as the direct and indirect food web effects of greater Anolis predation pressure on arthropods following brown anole invasion. Larger-bodied ground and foliage-dwelling arthropods tended to be negatively associated with brown anole abundance, as was total foliage arthropod abundance; by contrast, smaller-bodied arthropods, which are less likely to serve as brown anole prey, tended to be positively associated with brown anole abundance. The abundances of arthropod-consuming birds were also negatively associated with brown anole abundance, possibly reflecting exploitative competition for prey. Although many of the observed patterns were partly or entirely co-explained by environmental and spatial covariables, both statistical evidence and mechanistic considerations strongly suggested that at least some arthropod response groups were differentially affected by green anole and brown anole populations. To evaluate the potential contribution of anole perching and foraging behavior to differential population-level effects, I compared the per-capita effects of male green and brown anoles for several arthropod prey taxa that were stocked, over a vi series of experiments, into field enclosures erected over small cabbage palms (Sabal palmetto). Despite significant differences in every measured behavioral attribute, male green and brown anoles had statistically indistinguishable effects on six of seven prey taxa, suggesting that individuals of these two species have similar per-capita effects on prey assemblages when they forage in spatially-proximate locations. This dissertation represents one of the few existing comparisons of the relative food web effects of terrestrial vertebrate predators. vii TABLE OF CONTENTS Chapter 1: Introduction .............................................................................................................. 1 Literature cited ......................................................................................................................... 13 Chapter 2: Arthropod community differences on islands dominated by native versus invasive Anolis lizards ..................................................................................................... 23 Abstract .................................................................................................................................... 24 Introduction .............................................................................................................................. 25 Methods.................................................................................................................................... 30 Results .....................................................................................................................................